Method of inhibiting smooth muscle cell proliferation

ABSTRACT

The present invention relates, in general, to vascular smooth muscle proliferation and, in particular, to a method of inhibiting arterial and venous smooth muscle proliferation resulting, for example, from arterial injury or vein grafting. The invention also relates to an expression construct encoding a Gβγ inhibitor suitable for use in such a method.

This is a continuation of application Ser. No. 08/943,208, filed Oct. 3, 1997, now U.S. Pat. No. 5,981,487 now pending, the entire content of which is hereby incorporated by reference in this application.

This application claims priority from U.S. provisional Application Ser. No. 60/027,775, filed Oct. 4, 1996, the entire contents of which is incorporated herein by reference.

This invention was made with Government support under Grant No. HL-15448 awarded by the National Institutes of Health (NIH). The Government has certain rights in the invention.

TECHNICAL FIELD

The present invention relates, in general, to vascular smooth muscle proliferation and, in particular, to a method of inhibiting arterial and venous smooth muscle proliferation resulting, for example, from arterial injury or vein grafting. The invention also relates to an expression construct encoding a Gβγ inhibitor suitable for use in such a method.

BACKGROUND

Several growth factors that induce cellular mitogenesis and proliferation act through membrane-embedded G protein-coupled receptors (GPCRs). GPCRs couple to, and stimulate, heterotrimeric G proteins which, upon activation, dissociate to Gα and Gβγ subunits. Both these molecules can transduce intracellular signals via activation of specific effect or proteins. The intracellular signaling events leading to cellular proliferation following GPCR-activation appear to be transduced largely through the activation of p21^(ras) (Ras) and subsequent activation of the p42 and p44 mitogen-activated protein (MAP) kinases. Growth factors which act through GPCRs, such as lysophosphatidic acid (LPA) via the LPA receptor and norepinephrine via α2-adrenergic receptors, have been shown to activate Ras and MAP kinase primarily through Gβγ (Koch et al, Proc. Natl. Acad. Sci. USA 91:12706 (1994)).

The last 194 amino acids (Gly⁴⁹⁵-Leu⁶⁸⁹) of the bovine β-adrenergic receptor kinase-1 (βARK-1) represent a specific and selective Gβγ-inhibitor (see FIG. 1 for amino acid sequence of βARK-1-(495-689) and a nucleic acid sequence encoding same). βARK-1 is a Gβγ-dependent, cytosolic enzyme which must translocate to the membrane where it can phosphorylate its receptor substrate by physically binding to the membrane-anchored Gβγ (Pitcher et al, Science 257:1264 (1992)).

The peptide encoded by the plasmid designated βARK-1-(495-689) Minigene (which peptide is designated βARK_(CT)) contains the specific Gβγ-binding domain of βARK-1 (Koch et al, J. Biol. Chem. 268:8256 (1993)). When cells are transfected with the βARK-1-(495-689) Minigene (that is, the βARK_(CT) Minigene), or peptides containing the Gβγ-binding domain of βARK-1 are introduced into cells, several Gβγ-dependent processes are markedly attenuated including βARK-1-mediated olfactory receptor desensitization (Boekhoff et al, J. Biol. Chem. 269:37 (1994)), phospholipase C-β activation (Koch et al, J. Biol. Chem. 269:6193 (1994)) and Gβγ-dependent activation of Type II adenylyl cyclase (Koch et al, Biol. Chem. 269:37 (1994)). These studies demonstrate that the βARK-1-(495-689) peptide (that is, βARK_(CT)) is Gβγ-specific, that is, that it does not alter Gα-mediated responses (Koch et al, Proc. Natl. Acad. Sci. USA 91:12706 (1994); Koch et al, Biol. Chem. 269:37 (1994)). A further study utilizing the βARK_(CT) Minigene has demonstrated that the growth factor IGF-1, by binding to its specific receptor, activates the Ras-MAP kinase pathway via Gβγ. These results indicate that certain receptor-tyrosine kinase-mediated cascades include a Gβγ component, as do those for LPA and other agonists that activate classical GPCRs (Luttrell et al, J. Biol. Chem. 270:16495 (1995)).

The present invention is based, at least in oart, on the observation that the βARK_(CT) peptide mediates inhibition of Gβγ function in vivo and that, in smooth muscle cells, that inhibition is associated with a modulation of cell proliferation.

OBJECTS AND SUMMARY OF THE INVENTION

It is a general object of the invention to provide a method of inhibiting smooth muscle proliferation.

It is a specific object of the invention to provide a method of inhibiting uncontrolled smooth muscle cell proliferation by inhibiting Gβγ-signaling.

It is another object of the invention to provide a method of reducing intimal hyperplasia following vein grafting and restenosis following arterial injury.

The foregoing objects are met by the method of the present invention which comprises introducing into smooth muscle cells at a body site an agent that inhibits Gβγ-mediated processes and thereby inhibits proliferation of the muscle cells. In one embodiment, the agent comprises a nucleic acid encoding a polypeptide corresponding to the Gβγ-binding domain of βARK. In accordance with this embodiment, the nucleic acid is introduced into the cells in a manner such that the polypeptide is produced and proliferation of the smooth muscle cells is inhibited.

Further objects and advantages of the invention will be clear from the description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Amino acid sequence of βARK_(CT) (that is, βARK-1-(495-689)) polypeptide and nucleic acid sequence encoding same (SEQ ID NO:2 and SEQ ID NO:1, respectively).

FIG. 2. RT PCR results from 3 day vein grafts treated with empty pRK5 and pRK βARK_(CT). Lane 1 Φ×174HaeIII digested DNA markers with 2 of the size marker positions listed at the left; lanes 2 and 3, two control vein grafts transfected with pRK5 (plasmid); lanes 4 and 5, two vein grafts transfected with pRK βARK_(CT); lane 6 negative control for PCR; lane 7, amplification of the positive control pRK βARK_(CT)purified plasmid. This gel displays two of each of the four 3 day vein grafts tested by RT PCR for transgene expression.

FIG. 3. MAP kinase activity in cultured vascular smooth muscle cells.

FIG. 4. Intima-to-media thickness ratio in rat carotid 28 days after balloon injury.

DETAILED DESCRIPTION OF THE INVENTION

Smooth muscle proliferation is problematic in several clinical settings including intimal hyperplasia following vein grafting (Davies and Hagen, Br. J. Surg. 81:1254 (1994)) and restenosis following arterial angioplasty (Epstein et al, J. Am. Coll. Cardiol. 23:1278 (1994); French et al, Circulation 90:2402 (1994)). Smooth muscle cell proliferation is also associated with the development of atherosclerotic lesions (Katsuda et al, Amer. J. Pathol. 142:1787 (1993)). Smooth muscle cell proliferation can also be a problem when it occurs in the airways (Schramm et al, Life Sci. 59:PL9 (1996)), for example, in asthmatic patients and in individuals with idiopathic pulmonary fibrosis (Kanematsu et al, Chest 105:339 (1994)). The present invention provides a method of controlling smooth muscle proliferation in such settings by inhibiting Gβγ-dependent processes.

More specifically, the present invention provides a method of inhibiting smooth muscle proliferation at a body site comprising introducing into smooth muscle cells at the site an agent that effects inhibition of Gβγ-mediated processes. In one embodiment, the agent is a nucleic acid sequence that encodes a polypeptide that specifically inhibits Gβγ-dependent processes. One such agent is a nucleic acid encoding the Gβγ-binding domain of βARK.

As one example, the present invention relates to a nucleic acid that encodes the last 194 amino acids of βARK-1, e.g., the amino acid sequence given in FIG. 1. Inhibitory portions of this polypeptide can also be used, for example, the 125 amino acid portion from position 546-670 of the FIG. 1 sequence (corresponding to amino acids 53-177 of SEQ ID NO:2) or the 28 amino acid portion from position 643-670 of the FIG. 1 sequence (corresponding to amino acids 150-177 of SEQ ID NO:2). Methods that can be used to identify βARK(1 and 2) fragments that inhibit Gβγ-dependent processes are described by Koch et al, J. Biol. Chem. 268:8256 (1993) (see also Touhara et al, J. Biol. Chem. 270:17000 (1995); Inglese et al, Proc. Natl. Acad. Sci USA 91:3637 (1994); Luttrell et al, J. Biol. Chem. 270: 16495 (1995); Hawes et al, J. Biol. Chem. 270:17148 (1995); Koch et al, Proc. Natl. Acad. Sci. USA 91:12706 (1994)). In one aspect of this example, the nucleic acid has the sequence also given in FIG. 1 (SEQ ID NO:1). Additionally, nucleic acids suitable for use in the present invention include those encoding functional equivalents of the polypeptide shown in FIG. 1 (SEQ ID NO:2), and portions thereof, that is, polypeptides that specifically inhibit binding of βARK to Gβγ.

In addition to the βARK fragments described above, fragments of the 33 Kda Gβγ-binding retinal phosphoprotein, phosducin, can also be used. Examples of fragments of phosducin suitable for use in the present invention, and methods of selecting same, are described by Xu et al, Proc. Natl. Acad. Sci. USA 92:2086 (1995) and Hawes et al, J. Biol. Chem. 269:29825 (1994). Suitable nucleic acid sequences encoding these peptides will be apparent to one skilled in the art.

In accordance with the present invention, the nucleic acid described above can be present in a recombinant molecule which can be constructed using standard methodologies. The recombinant molecule comprises a vector and the nucleic acid encoding the inhibitor. Vectors suitable for use in the present invention include plasmid and viral vectors. Plasmid vectors into which the nucleic acid can be cloned include any plasmid compatible with introduction into smooth muscle cells. Such vectors include mammalian vectors such as pRK5. Viral vectors into which the nucleic acid can be introduced include adenoviral vectors (see Examples II and III), retroviral vectors, and adenoassociated viral vectors. The nucleic acid of the invention can be present in the vector operably linked to regulatory elements, for example, a promoter. Suitable promoters include, but are not limited to, the CMV, TK and SV40 promoters. Smooth muscle cell specific promoters can also be used, for example, an αSM22 promoter (see Moessler et al, Develop. 122:2415 (1996)).

In another embodiment of the present invention, a Gβγ inhibitor can be introduced directly into smooth muscle cells at a target site using methodologies known in the art. One such inhibitor is the polypeptide corresponding to the Gβγ-binding domain of βARK, for example, amino acids Gly⁴⁹⁵-Leu⁶⁸⁹ of βARK-1. Other suitable peptides of both βARK and phosducin are described above as are references disclosing methods suitable for use in selecting inhibitory peptides. The Gβγ inhibitor can be introduced into the target cells in a form substantially free of any proteins with which it may normally be associated. Polypeptide inhibitors can be produced recombinantly using the nucleic acid described above or chemically using known methods.

Compositions

The present invention also relates to pharmaceutically acceptable compositions comprising the nucleic acid or polypeptide of the invention. Such compositions can include, as active agent, the inhibitor or inhibitor-encoding sequence, in combination with a pharmaceutically acceptable carrier (e.g., water, phosphate buffered saline, etc.). The amount of active agent present in the composition can vary with the inhibitor or encoding sequence, the delivery system (in the case of a nucleic acid), the patient and the effect sought. Likewise, the dosing regimen can vary depending, for example, on the delivery system (particularly when a nucleic acid is used), the composition and the patient.

Therapy

The present invention relates to the use in gene therapy regimens of a nucleic acid (e.g., a DNA sequence) encoding a Gβγ inhibitor, for example, a polypeptide corresponding to the βARK Gβγ-binding domain, or portions thereof as defined above.

Delivery of the nucleic acid of the invention can be effected using any of a variety of methodologies, including transfection with a plasmid or viral vector, such as those described above (see, for example, Steg et al, Circulation 90:1640 (1994), Guzman et al, Circulation 88:2838 (1993), Lee et al, Circulation Res. 73:797 (1993) and Plautz et al, Circulation 83:578 (1991)), or fusion with a lipid (e.g., a liposome) (see Takeshita et al, J. Clin. Invest. 93:652 (1994), Chapman et al, Cir. Res. 71:27 (1992), LeClerc et al, J. Clin. Invest. 90:936 (1992) and Nabel et al, Human Genet. 3:649 (1992)). Upon introduction into target cells, the nucleic acid is expressed and the Gβγ inhibitor is thereby produced.

Target cells include smooth muscle cells present, for example, in veins, arteries or airways.

Introduction of the nucleic acid into the target cells can be carried out using a variety of techniques. In the case of vein grafting, the techniques set forth in Examples I and II that follow can be used. As described in Example I, prior to grafting, the vein graft can be contacted with a solution containing the nucleic acid encoding the Gβγ inhibitor. While in Example I the nucleic acid is present in an plasmid, other systems can be used to effect delivery, including those described above and in Example II. Alternatively, naked nucleic acid (e.g., naked DNA) present in a pharmaceutically acceptable carrier can be used.

In accordance with the present method, the graft is held in contact with the nucleic acid for a period of time (e.g., 20-30 minutes) sufficient to permit introduction of the nucleic acid into smooth muscle cells of the graft and under conditions that facilitate the introduction of the nucleic acid without unacceptably compromising viability of the graft. Optimum conditions can readily be determined by one skilled in the art (see Examples I and II below).

In the case of arterial smooth muscle cells, the nucleic acid, advantageously in a viral vector, can be administered to an actual injury site (including an atherosclerotic site) via a catheter, for example, a balloon catheter. In accordance with this approach, inhibition of restenosis following angioplasty can be effected as can inhibition of smooth muscle cell proliferation at other arterial injury (or atherosclerotic) sites. (See Example III.)

As indicated above, other target sites include airway smooth muscle cells. Nucleic acids of the invention can be delivered to such cells, for example, in a viral vector, via aerosol administration. Optimum conditions can be readily determined by one skilled in the art.

The therapeutic methodologies described herein are applicable to both humans and non-human mammals.

It will be appreciated from a reading of this disclosure that the present invention makes possible a variety of studies targeting G protein pathways. Further therapeutic modalities can be expected to result from such studies.

Screening

The demonstration that βARK_(CT) inhibits smooth muscle cell proliferation makes possible assays that can be used to identify other smooth muscle cell proliferation inhibitors. For example, compounds to be tested for their ability to inhibit smooth muscle cell proliferation can be contacted with a solution containing Gβγ (eg purified Gβγ)and βARK, or a Gβγ binding portion thereof (eg purified βARK, or portion thereof), under conditions such that binding of Gβγ and βARK, or binding portion thereof, can occur. Test compounds that inhibit that binding can be expected to inhibit smooth muscle cell proliferation. Such tests compounds can also be screened for their ability to inhibit smooth muscle cell proliferation by determining the effect of the presence of the compound on Gβγ activation of βARK (eg using standard methodologies). A test compound that inhibits kinase activation can be expected to be suitable for use as an inhibitor of smooth muscle cell proliferation. Test compounds can also be screened by contacting cells (eg smooth muscle cells or fibroblasts) with such a compound and determining the effect of the test compound on LPA dependent activation of MAP kinase. A test compound that inhibits such activation can be expected to inhibit smooth muscle cell proliferation.

Certain aspects of the present invention are described in greater detail in the non-limiting Example that follows.

EXAMPLE I Effect of βARK_(CT) on the Formation of Vein Graft Intimal Hyperplasia and Phenotypical Functional Alterations

Experimental design: Forty New Zealand White rabbits underwent carotid interposition vein bypass grafting. Prior to grafting, veins were incubated in heparinized Ringer's lactate (controls; n=18), or plasmid solutions containing either βARK_(CT) (n=14; 190 μg/ml) or empty plasmid DNA (plasmid: n=8; 190 μg/ml) for 30 mins at 37° C. Twenty-four vein grafts (n=10 controls, n=6 plasmid, n=8 βARK_(CT)) were harvested at 28 days by perfusion fixation. Intimal and medial dimensions of vein grafts were calculated by videomorphometry. Sections were taken for scanning and transmission electron microscopy (TEM). Ten vein grafts (n=5; control and βARK_(CT)) were analyzed for in vitro contractile responses to norepinephrine and serotonin in the presence and absence of pertussis toxin (PTx) to categorize receptor G-protein receptor coupling. Six vein grafts (n=3; control and βARK_(CT)) were harvested at 3 days for βARK-1 protein and mRNA (RT-PCR) expression.

Transgene constructs: Gene transfer to the experimental vein grafts was done utilizing the previously described plasmid which contains cDNA encoding the last 194 amino acid residues (Met-Gly⁴⁹⁵-Leu⁶⁸⁹) (SEQ ID NO:2) of bovine βARK_(CT) (PRK-βARK_(CT)) (Koch et al, Proc. Natl. Acad. Sci. USA 91:12706 (1994); Koch et al, J. Biol. Chem. 268: 8256 (1993)). This peptide contains the experimentally determined (Gln⁵⁴⁶-Ser⁶⁷⁰) (corresponding to amino acids 53-177 of SEQ ID NO:2) Gβγ binding domain. The empty pRK5 plasmid was used as the negative control as previously described (Koch et al, Proc. Natl. Acad. Sci. USA 91:12706 (1994); Koch et al, J. Biol. Bhem. 269:6193 (1994)). Large scale plasmid preparations of pRK5 and pRK βARK_(CT) were purified using Qiagen columns (Qiagen Inc., Chatsworth, Calif.) prior to vein graft gene transfer.

Analysis Of βARK_(CT) transgene expression: Three day vein grafts were utilized for analysis of specific transgene expression. βARK_(CT) mRNA expression was determined by standard methods of reverse transcriptase-polymerase chain reaction (RT-PCR) (Ungerer et al, Circularion 87:454 (1993)) using a RT-PCR kit utilizing TaqPlus DNA Polymerase (Stratagene Inc. La Jolla, Calif.). Total RNA was first isolated using the single step reagent RNAzol (Biotecx Inc., Houston, Tex.) (Chomezynski et al, Anal. Biochem. 161: 156 (1987))) and treated with DNase I to eliminate any possible plasmid contamination. A βARK_(CT) primer set was utilized to specifically amplify βARK_(CT) mRNA. The primers utilized were as follows: sense primer (corresponding to the start of βARK_(CT)) 5′-GAATTCGCCGCCACCATGGG-3′ (SEQ ID NO:3); antisense primer (corresponding to the β-globin untranslated region linked to the end of the βARK_(CT) cDNA (Koch et al, J. Biol. Chem. 269:6193 (1994)) 5′-GGAACAAAGGAACCTTTAATAG-3′ (SEQ ID NO:4). This primer set amplifies a 670 base pair fragment corresponding to βARK_(CT) mRNA.

Operative Procedure: Anesthesia was induced and maintained with subcutaneously injected ketamine hydrochloride (60 mg/kg, Ketaset, Bristol Laboratories, Syracuse, N.Y.) and xylazine (6 mg/kg, Anased, Lloyd Laboratories, Shenandoah, Iowa). Antibiotic prophylaxis with 30,000 IU/kg of benzanthine and procaine penicillin (Durapen, Vedco Inc., Overland Park, Kans.) was given intramuscularly at the time of induction. Surgery was performed using an operating microscope (JKH 1402, Edward Weck Inc., Research Triangle Park, N.C.) under sterile conditions. After exposure through a midline longitudinal neck incision, the right external jugular vein was identified, its branches were diathermied at a distance from the vein to minimize injury and it was then dissected out. Following excision, the vein was kept moist in a heparinized Ringer lactate solution (5 IU/ml, Heparin, Elkins-Sinn Inc., Cherry Hill, N.J.) for approximately 15 minutes while the right common carotid artery was identified, dissected and both proximal and dismal control obtained. Heparin (200 IU/kg) was administered intravenously. A proximal longitudinal arteriotomy was made and one end of the reversed jugular vein was anastomosed to the artery in an end-to-side manner using continuous 10-O microvascular monofilament nylon suture (Ethilon, Ethicon Inc., Somerville, N.J.). The distal anastomosis was performed in a similar manner. Throughout the procedure, care was taken to avoid unnecessary instrumentation of the vein graft. The right common carotid was ligated and divided between the two anastomoses with 4-O silk sutures and the wound closed in layers.

Morphology: Three vein grafts were harvested 28 days after surgery. Following isolation and systemic heparinization (200 IU/kg, i.v.), the vein grafts were perfusion fixed in situ at 80 mmHg with an initial infusion of Hanks Balanced Salt Solution (HBSS, Gibco Laboratories, Life Technologies Inc., Grand Island, N.Y.) followed by 2% glutaraldehyde made up in 0.1 M cacodylate buffer (pH 7.2) supplemented with 0.1 M sucrose to give an osmolality of approximately 300 mOsm. After 60 minutes, the specimen was removed, immersed in the glutaraldehyde fixative for a further 24 hours. Cross-sections from the mid-portion of the vein graft were processed for light microscopy. Following standard histological procedures, each specimen was stained with a modified Masson's trichrome and Verhoeff's elastin stain and dimensional analysis was performed by videomorphometry (Innovision 150, American Innovision Inc., San Diego, Calif.). The intima and media were delineated by identification of the demarcation between the criss-cross orientation of the intimal hyperplastic smooth muscle cells and circular smooth muscle cells of the media and the outer limit of the media was defined by the interface between the circular smooth muscle cells of the media and the connective tissue of the adventida. The thickness of each layer was also determined. A ratio of the intimal and medial areas (intimal ratio=intimal area/[intimal+medial areas]) and a luminal diameter to cross-sectional wall thickness (luminal index=luminal diameter/[cross-sectional wall thickness]) was calculated.

In vitro contractile studies: Under anesthesia, the original incision was re-opened and the jugular vein and vein graft isolated. The midpart of each vessel was sectioned in situ into two 5 mm segments and excised. These rings were suspended immediately from two stainless steel hooks in 5 ml organ baths containing oxygenated Krebs solution (122 mM NaCl, 4.7 mM KCl, 1.2 mM MgCl₂, 2.5 mM CaCl₂, 15.4 mM NaHCO₃, 1.2 mM KH₂PO₄ and 5.5 mM glucose; maintained at 37° C. and bubbled with a mixture of 95%) O₂ and 5% CO₂) . One hook was fixed to the bottom of the bath and the other was connected to a force transducer (Myograph F-60, Narco Bio-Systems, Houston, Tex.) . The isometric responses of the tissue were recorded on a multichannel polygraph (Physiograph Mk111-S, Narco Bio-Systems, Houston, Tex.) . The tissues were then placed under 0.5 grams tension and allowed to equilibrate in physiologic Krebs solution for one hour. During the equilibration period, the Krebs solution was replaced every 15 minutes. Following equilibration, the resting tension was adjusted in 0.25 gram increments from 0.25 to 2.5 gram and the maximal response to a modified oxygenated Krebs solution (60 mM KCl, 66.7 mM NaCl, 1.2 mM MgCl₂, 2.5 mM CaCl₂, 15.4 mM NaHCO₃, 1.2 mM KH₂PO₄ and 5.5 mM glucose) was measured at each resting tension to establish a length-tension relationship. Based on these results, the optimal resting tension for each ring (the tension at which the response to the modified Krebs solution was maximal) was determined and the ring was set at this tension for subsequent studies. Norepinephrine (10⁻⁹ to 10⁻⁴M) was added cumulatively in half molar increments and the isometric tension developed by the tissue was measured. After washout and re-equilibration, dose response curves were obtained for serotonin (10⁻⁹ to 10⁻⁴M). The responses to each agonist were assessed with and without the presence of PTx (100 ng/ml pre-incubated for 60 minutes) (Davies et al, J. Clin. Invest. 94:1680 (1994)). All compounds were obtained from Sigma Chemical Company (St. Louis, Mo.).

Data and Statistical Analysis: The EC₅₀ value, the concentration for the half maximal response, for each agonist in each ring was calculated by logistic analysis and is expressed as loglo [EC₅₀] (Finney, Statistical methods in biological assay. London: Charles Griffin, pp. 349-369 (1978)). All data are presented as the mean±standard error of the mean (s.e.m.) and statistical differences between groups were tested by ANOVA with post hoc Tukey-Kramer multiple comparison tests for the functional studies and with a Kruskal-Wallis nonparametric ANOVA with post hoc Dunn's multiple comparison tests for the morphometric data.

Results

Transgene expression: Successful transfection of the vein grafts was demonstrable at three days after surgery. βARK_(CT) mRNA was specifically amplified from DNase I treated total RNA using RT-PCR from vein grafts treated with pRK- βARK_(CT) while control grafts treated with the empty pRK5 plasmid showed no transgene expression (FIG. 2). Since the amount of tissue available is small, protein immunoblotting for βARK_(CT) peptide expression was not possible.

Intimal hyperplasia: All animals survived to 28 days, and all grafts were patent at harvest. Microscopically, the luminal surfaces of the vein grafts from each group were covered by a layer of intact endothelial cells, beneath which lay a hyperplastic intima with the smooth muscle cells of the intimal hyperplasia arranged in a crisscross pattern with little extracellular matrix. The medial smooth muscle cells in the grafts from each group appeared slender, were arranged in a circular pattern, and contained a greater amount of extracellular matrix suggestive of medial hypertrophy. At 28 days, there was a significant 37% reduction in intimal thickness in βARK_(CT) vein grafts (45±4 μm) compared to either plasmid (69±3 μm) or control (70±4 μm) vein grafts without a significant change in medial thickness (70±4 μm, 65±5 μm and 77±3 μm, respectively). Dimensional analysis of the control and treated groups is shown in Table I. There was a 52% decrease in intimal area (Table I) while the medial area was unchanged in the βARK_(CT) compared to the plasmid treated vein grafts (Table I). The intimal ratio was significantly reduced in the βARK_(CT) vein grafts (p<0.01; 0.36±0.02, mean±s.e.m.) compared to either plasmid (0.54±0.02) or control vein grafts (0.52±0.02). The luminal area of the βARK_(CT) treated vein grafts was 41% less than the plasmid treated vein grafts while the luminal indices were not significantly different for the control, plasmid and βARK_(CT) vein grafts.

TABLE I Dimensional Analysis Control Plasmid βARK_(CT) p-value Lumen (mm²) 20.5 ± 1.5 28.6 ± 4.01 16.6 ± 2.33† 0.02 Intima (mm²) 1.14 ± 0.09 1.29 ± 0.12 0.62 ± 0.03† 0.01 Media (mm²) 1.08 ± 0.11 1.29 ± 0.17 1.12 ± 0.10 0.18 Intimal ratio 0.52 ± 0.02 0.54 ± 0.02 0.36 ± 0.02* 0.02 Luminal Index 39.4 ± 2.6 44.2 ± 3.1 37.8 ± 3.9 0.4 The area of the lumen, the intimal and the medial layers from control, plasmid and βARK_(CT) treated grafts. The intima ratio (intimal area/[intimal + medial areas]) and luminal index (luminal diameter/[cross-sectional wall thickness]) are also shown. Values are the mean ± s.e.m. Statistical Analysis is by Kruskal-Wallis nonparametric ANOVA with post hoc Dunn's multiple comparison tests (p < 0.05 vs. Control; †p < 0.05 vs. Plasmid)

 

Contractile function of experimental vein grafts: Control and βARK_(CT) treated vein grafts responded with concentration dependent contractions to the agonists norepinephrine and serotonin. In the presence of PTx at concentrations sufficient to produce 100% ADP ribosylation of G-proteins (Davies et al, J. Clin. Invest. 94:1680 (1994)), the contractile responses in control vein grafts to norepinephrine (p<0.01) and serotonin (p<0.01) were significantly reduced compared to untreated control vein grafts (Table II). This is the typical functional alteration seen in experimental vein grafts as native veins do not have a PTx sensitive component in their contractile responses to these G-protein coupled agonists. In contrast, the responses of the βARK_(CT) treated vein grafts to norepinephrine and serotonin were unchanged in the presence of PTx indicating the loss of a Gα_(i) component (Table II).

TABLE II Sensitivity of Contractile Responses Norepinephrine Serotonin with per- with per- Norepinephrine tussis toxin Serotonin tussis toxin Control 6.00 ± 0.09 5.16 ± 0.09* 6.34 ± 0.10 5.54 ± 0.26* βARK_(CT) 5.91 ± 0.19 5.81 ± 0.18 6.57 ± 0.10 6.55 ± 0.13 Data are expressed s the mean ± s.e.m.. Contractile sensitivity is shown as -logEC₅₀. *p < 0.01 compared to corresponding pertussis toxin untreated vessel by ANOVA.

Electron microscopy of vein grafts: Scanning electron microscopy from both control vein grafts and vein graft transfected with empty plasmid showed the luminal surface to be lined with sharply outlined endothelial cells with well defined cell borders. Occasional junctional stomata were noted. Transmission electron micrograph of these vein grafts confirmed the presence of well formed endothelial cells, beneath which were well developed smooth muscle cells of both contractile (cytoplasm predominantly filled with contractile filaments) and synthetic phenotypes (cytoplasm filled with synthetic organelles) in a loose connective tissue matrix. No inflammatory cells or evidence for apoptosis was identified in these grafts. Scanning electron microscopy from vein grafts transfected with βARK_(CT) showed a similar picture to the control and plasmid transfected vein grafts with well preserved, normal appearing endothelial cells with occasional stomata at their junctions on the luminal surface. Transmission electron microscopy showed a similar ultrastructural pattern to the control and plasmid transfected vein grafts. One difference in the βARK_(CT) treated vein grafts was seen at higher magnification, which was the appearance of numerous cells with ultrastructural evidence of apoptosis with nuclear fragmentation, membrane disruption, and in places, disintegration products consisting of endoplasmic reticulum.

EXAMPLE II Adenoviral Mediated Inhibition of Gβγ Signaling Limits Development of Intimal Hyperplasia

Thirty-seven male NZW rabbits had interposition bypass grafting of the carotid artery using the jugular vein. Prior to grafting, veins were incubated in heparinized Ringer's lactate (controls; n=10), solutions containing adenoviral vectors (1×10¹⁰ PFU/ml) encoding βARK_(CT) (n=19), β-galactosidase (β-Gal; n=3), or empty vector (EV; n=3). (For details of adenoviral vector, see Drazner et al., J. Clin. Invest. 99:288 (1997).) After implantation, vein grafts were coated with 4 ml of 30% pluronic gel with or without the respective viral solutions (1.7×10⁹ PFU/ml).

The efficacy of βARK_(CT) transfection in vein grafts was verified by RT-PCR on days 3, 5 and 7 postoperatively (n=3 per time-point). To determine the cellular expression of the transfected gene, X-Gal staining for the marker gene β-Gal was performed on day

3. Positive (blue) cells were seen throughout the wall of the β-Gal vein grafts. At 28 days, the intimal thickness) in βARK_(CT) vein grafts (n=6) was reduced by 33% with no significant change in the medial thickness (MT), compared to control (n=6) and EV (n=3) grafts (Table III). Contractile studies showed enhanced sensitivity in response to norepinephrine (NE) and serotonin (5-HT) in 28 day βARK_(CT) vein grafts (n=4), as compared to controls (n=4) and EV (n=2), and insensitivity to pertussis toxin (PT) (Table III). Viral infection of vein grafts with EV did not alter vein grafts dimensions or contractility.

TABLE III IT (μm) MT (μm) NE NE + PT 5-HT 5-HT + PT βARK_(CT) 57 ± 4* 68 ± 3 6.35 ± 0.06† 5.92 ± 0.25 6.74 ± 0.10† 6.46 ± 0.19 EV 86 ± 10 87 ± 4 5.67 ± 0.03 — 5.65 ± 0.08 — Control 85 ± 4 91 ± 5 5.85 ± 0.10 5.17 ± 0.14‡ 6.17 ± 0.10 5.32 ± 0.18‡ Data are shown as mean ± S.E.M. Sensitivity is defined as -logED₅₀. *p < .05 compared to EV and control (Kruskal-Wallis with post-hoc Dunn's test); †p < .01 compared to EV and control (ANOVA); ‡p < .001 compared to without PT (Student t-test).

The results demonstrate that inhibition of Gβγ signaling with adenoviral mediated βARK_(CT) in vivo transfection effectively modifies the structural and functional hyperplastic abnormalities in experimental vein grafts.

EXAMPLE III Inhibition of Restenosis of Injured Carotid Artery with βARK_(CT) Adenovirus

The rat common carotid injury is a well studied and reliable model of neo-initimal cell proliferation (Clowes et al, Lab. Invest. 49:327 (1983)). Following the application of a high pressure vascular damage, vascular smooth muscle cells migrate from the tunica media through the basal lamina into the tunica intima, were they proliferate. Those mechanisms are sustained by growth factor released from cells infiltrating the neo-intima and other substances circulating in the blood stream. At the vascular smooth muscle cells level, those factors interact with specific receptors thus activating intracellular mechanisms of proliferation. Among them, mitogen activated protein (MAP) kinase plays a relevant role, being at the confluence of several receptor activated pathways. It has been demonstrated recently that the βγ subunit of the heterotrimeric G protein mediates the activation of the MAP kinase induced by Gi coupled receptors. The carboxyterminus portion of the G coupled receptor kinase βARK1 binds the βγ subunit, thus inhibiting its signaling on MAP kinase.

Using adenoviral mediated gene delivery (see Drazner et al., J. Clin. Invest. 99:288 (1997), it was possible to demonstrate that induction of expression of βARK_(CT) resulted in the inhibition of proliferation of vascular smooth muscle cells in the rat carotid injury model. Firstly, it was shown that in rabbit aortic smooth cells in culture (see Davies et al, J. Surg. Res. 63:128 (1996)), the virus was able to infect and replicate, resulting in the inhibition of the activation of MAP kinase in response to Gi coupled receptor stimulation. The lysophosphatidic receptor, a major mitogen circulating in the serum, was assessed. Furthermore, MAP kinase activation in response to fetal bovine serum and epidermal growth factor was assessed. βARK_(CT) adenovirus in the cultured vascular smooth muscle cells inhibited LPA (−58% of the same response observed in empty virus treated cells) and serum (−38%) activation of MAP kinase, without interfering with basal (+18%) and EGF (−7%) response (see FIG. 3).

The feasibility of infection of vascular smooth muscle cells in vivo was also determined using the rat common carotid after balloon injury. The balloon injury was performed through the external carotid in the common carotid by means of a Fogarty catheter with the balloon inflated at 1.5 atmospheres. After the injury, the virus (0.5×10¹⁰ PFU) was injected into the lumen of the common carotid through the external carotid and incubated for 30 min. The external carotid was then tied up by means of silk sutures and the blood flow in the common carotid was restored. A further dose of virus (˜0.5×10¹⁰ PFU) was applied at the external of the common carotid by means of pluronic gel. The wound was closed in layers. A virus containing the bacterial gene LAC-Z encoding β-galactosidase was used, and after three days from the injury and the application of the virus, β-Gal staining was performed on cyo-fixed carotid arteries. The staining demonstrated that the application of the virus from the lumen and the external by means of the pluronic gel resulted in the infection of the arterial wall from the intima throughout the adventitia.

Successively, using the same protocol, it was determined whether the virus encoding the βARK_(CT) was able to replicate in the carotid. After five days from the injury and the application of the virus, RT-PCR was performed on DNAse treated RNA extracted from rat common carotids. This analysis allowed testing of the efficacy of the virus to replicate in vivo.

In a further set of experiments, injured common carotid was treated with βARK_(CT), or empty virus. After 28 days, the carotids were harvested and fixed and analyzed for morphometric measurements. A intimal proliferation index was obtained by the intima-to-media thickness ratio. In animals treated with empty virus, the intima proliferation was 2.036±0.312, while in the βARK_(CT) treated carotid, this ratio was 0.426±0.137, significantly reduced as compared to the empty virus treatment (p<0.01) (see FIG. 4).

All documents cited above are hereby incorporated in their entirety by reference.

One skilled in the art will appreciate from a reading of this disclosure that various changes in form and detail can be made without departing from the true scope of the invention.

4 591 base pairs nucleic acid single linear DNA (genomic) linear 1 ATGGGAATCA AGCTACTGGA CAGTGACCAG GAGCTCTACC GCAACTTCCC CCTGACCATC 60 TCGGAGCGGT GGCAGCAGGA GGTAGCAGAG ACTGTCTTTG ACACCATCAA TGCTGAGACG 120 GACCGGCTGG AGGCCCGCAA GAAAACCAAA AACAAGCAGT TGGGCCACGA GGAAGACTAC 180 GCCCTGGGCA AGGACTGCAT CATGCATGGC TACATGTCCA AGATGGGCAA CCCCTTCCTG 240 ACCCAGTGGC AGCGGCGGTA CTTCTACCTG TTCCCTAACC GGCTCGAGTG GCGGGGCGAG 300 GGCGAGGCCC CGCAGAGCCT GCTGACCATG GAGGAGATCC AGTCGGTGGA GGAGACGCAG 360 ATCAAGGAGC GAAAGTGCCT CCTCCTCAAG ATCCGAGGTG GCAAGCAGTT TGTCCTGCAG 420 TGCGATAGTG ACCCAGAGCT GGTGCAGTGG AAGAAGGAGC TTCGAGACGC CTACCGCGAG 480 GCCCAGCAGC TAGTGCAGCG GGTGCCCAAG ATGAAGAACA AGCCGCGCTC GCCCGTCGTG 540 GAGCTGAGCA AGGTGCCACT GATCCAGCGC GGCAGTGCCA ACGGCCTCTG A 591 196 amino acids amino acid <Unknown> linear protein linear 2 Met Gly Ile Lys Leu Leu Asp Ser Asp Gln Glu Leu Tyr Arg Asn Phe 1 5 10 15 Pro Leu Thr Ile Ser Glu Arg Trp Gln Gln Glu Val Ala Glu Thr Val 20 25 30 Phe Asp Thr Ile Asn Ala Glu Thr Asp Arg Leu Glu Ala Arg Lys Lys 35 40 45 Thr Lys Asn Lys Gln Leu Gly His Glu Glu Asp Tyr Ala Leu Gly Lys 50 55 60 Asp Cys Ile Met His Gly Tyr Met Ser Lys Met Gly Asn Pro Phe Leu 65 70 75 80 Thr Gln Trp Gln Arg Arg Tyr Phe Tyr Leu Phe Pro Asn Arg Leu Glu 85 90 95 Trp Arg Gly Glu Gly Glu Ala Pro Gln Ser Leu Leu Thr Met Glu Glu 100 105 110 Ile Gln Ser Val Glu Glu Thr Gln Ile Lys Glu Arg Lys Cys Leu Leu 115 120 125 Leu Lys Ile Arg Gly Gly Lys Gln Phe Val Leu Gln Cys Asp Ser Asp 130 135 140 Pro Glu Leu Val Gln Trp Lys Lys Glu Leu Arg Asp Ala Tyr Arg Glu 145 150 155 160 Ala Gln Gln Leu Val Gln Arg Val Pro Lys Met Lys Asn Lys Pro Arg 165 170 175 Ser Pro Val Val Glu Leu Ser Lys Val Pro Leu Ile Gln Arg Gly Ser 180 185 190 Ala Asn Gly Leu 195 20 base pairs nucleic acid single linear DNA (genomic) linear 3 GAATTCGCCG CCACCATGGG 20 22 base pairs nucleic acid single linear DNA (genomic) linear 4 GGAACAAAGG AACCTTTAAT AG 22 

What is claimed is:
 1. A method of inhibiting proliferation of smooth muscle cells comprising introducing into said cells an inhibitor of Gβγ-mediated proliferative signaling in an amount and under conditions such that said inhibition of proliferation is effected.
 2. The method of claim 1 wherein said smooth muscle cells are vascular smooth muscle cells.
 3. The method according to claim 2 wherein said vascular cells are present in a vein graft.
 4. The method according to claim 2 wherein said vascular cells are present at a carotid artery injury site.
 5. The method according to claim 2 wherein said vascular cells are present at a vein graft site.
 6. The method of claim 1 wherein said smooth muscle cells are airway smooth muscle cells.
 7. The method of claim 1 wherein said smooth muscle cells are mammalian cells.
 8. A method of screening a test compound for its ability to inhibit smooth muscle cell proliferation comprising: contacting said test compound with βARK and Gβγ, and determining whether said test compound inhibits binding of βARK to Gβγ, wherein inhibition by said test compound of said binding is indicative of a compound that can effect said inhibition of smooth muscle cell proliferation.
 9. The method according to claim 8 wherein said determination is effected by determining whether said test compound inhibits Gβγ activation of βARK.
 10. A method of inhibiting pathologic proliferation of intimal vascular smooth muscle cells comprising introducing into said cells an inhibitor of Gβγ-mediated proliferative signaling in an amount and under conditions such that said inhibition of proliferation is effected.
 11. A method of inhibiting proliferation of mammalian smooth muscle cells comprising introducing into said cells an inhibitor of Gβγ-mediated proliferative signaling in an amount and under conditions such that said inhibition of proliferation is effected, wherein said inhibitor binds Gay and thereby inhibits said Gβγ-mediated proliferative signaling.
 12. The method according to claim 11 wherein said inhibitor is a polypeptide.
 13. The method according to claim 12 wherein a nucleic acid sequence encoding said polypeptide is introduced into said cells under conditions such that said nucleic acid is expressed and said polypeptide is thereby produced.
 14. The method according to claim 11 wherein said smooth muscle cells are vascular smooth muscle cells.
 15. The method according to claim 14 wherein said vascular smooth muscle cells are present in a vein graft.
 16. The method according to claim 14 wherein said vascular smooth muscle cells are present at a carotid artery injury site.
 17. The method according to claim 14 wherein said vascular smooth muscle cells are present at a site of insertion of a vein graft.
 18. The method according to claim 11 wherein said smooth muscle cells are airway smooth muscle cells.
 19. A method of inhibiting pathologic proliferation of mammalian intimal vascular smooth muscle cells comprising introducing into said cells an inhibitor of Gβγ-mediated proliferative signaling in an amount and under conditions such that said inhibition of proliferation is effected, wherein said inhibitor binds Gβγ and thereby inhibits said Gβγ-mediated proliferative signaling.
 20. The method according to claim 19 wherein said inhibitor is a polypeptide.
 21. The method according to claim 20 wherein said polypeptide is the Gβγ binding domain of βARK.
 22. The method according to claim 20 wherein a nucleic acid sequence encoding said polypeptide is introduced into said cells under conditions such that said nucleic acid is expressed and said polypeptide is thereby produced.
 23. The method according to claim 20 wherein said polypeptide has the amino acid sequence set forth in SEQ ID NO:2 or portion thereof that includes at least amino acids 150-177 of said SEQ ID NO:2 sequence.
 24. The method according to claim 1 wherein said inhibitor is a polypeptide.
 25. The method according to claim 24 wherein a nucleic acid sequence encoding said polypeptide is introduced into said cells under conditions such that said nucleic acid is expressed and said polypeptide is thereby produced.
 26. The method according to claim 24 wherein said polypeptide has the amino acid sequence set forth in SEQ ID NO:2 or portion thereof that includes at least amino acids 150-177 of said SEQ ID NO:2 sequence. 